For ecological reasons, the current trend in hair spray cans is systematically to replace halogenated propellant gases of the Freon type by hydrocarbons, in particular by propane, butane, or mixtures thereof. However, this substitution cannot be made without profoundly changing the formulations both as concerns the ratios between the ingredients and as concerns the actual nature of the ingredients, particularly the film-forming substances. It is well known that an aerosol hair spray must meet certain criteria. Among these, the hair control properties in a highly moist atmosphere without the hair being observed to become sticky should be mentioned in particular.
Between two shampooings, the hair should retain good cosmetic properties to the touch, should not become sticky or greasy, and the hairs should untangle easily without clinging to each other, particularly when the shampooings are at least a week apart.
It is also important for the film-forming substance to be easily eliminated when the hair is washed. Finally, after application of the aerosol spray, the hair should look natural and it should be possible to comb it without formation of powder.
All these properties have been demonstrated for certain polymers which have been used for making aerosol sprays whose propellant was essentially a mixture of halogenated hydrocarbons, in particular mixtures of monofluorotrichloromethane and dichlorodifluoromethane.
Polymers such as those based on vinyl acetate and crotonic acid have, however, proved to be unusable in the presence of non-halogenated propellant gases.
Hence, recent work has focused on the choice of new polymers that might not only be compatible with nonhalogenated propellant gases but also have excellent cosmetic properties.
In this connection, one may cite European Patent Number 0,062,002, which describes a hair control composition containing, as the film-forming substance, a terpolymer resulting from copolymerization of:
a) 40 to 60 wt.% of an N-alkylacrylamide or an N-alkyl methacrylamide with 1 to 4 carbon atoms in the alkyl part, with PA1 b) 35 to 50 wt.% of a C.sub.1 -C.sub.4 alkyl ester or a C.sub.1 -C.sub.4 hydroxyalkyl ester of acrylic acid or methacrylic acid, and PA1 c) 3 to 11 wt.% of acrylic acid or methacrylic acid relative to the total monomer mixture and a proportion of at least 50% of carboxyl groups present in the terpolymer being neutralized by a lower organic base chosen from 2-amino-2-methyl-propanol, 2-amino-2-methyl-1,3-propanediol, triethanolamine, and triisopropanolamine, the propellant gas being a non-halogenated hydrocarbon such as propane or butane or a mixture thereof. PA1 (a) 5 to 10 wt.% acrylic acid (AA), preferably 5 to 8 wt.%; PA1 (b) 20 to 52 wt.% N,N-dimethylacrylamide (DMA), preferably 25 to 45 wt.%; PA1 (c) 3 to 28 wt.% N-tert-butylacrylamide (NtBA), preferably 5 to 25 wt.%; and PA1 (d) 20 to 45 wt.% ethyl methacrylate (EMA), preferably 25 to 40 wt.%; PA1 the carboxylic acid functions of said tetrapolymer being partially or totally neutralized with a mineral or organic base; and PA1 at least one non-halogenated compound as a propellant gas.
Although the choice of monomers of this terpolymer gave good compatibility with non-halogenated hydrocarbons, it was, however, found that some of the cosmetic properties of the aerosol sprays were not totally satisfactory.
In particular, the spray was observed to be insoluble when shampooed and sometimes the hair became very sticky about seven days after the application of the spray.